Perovskite halides (e.g., CH3NH3PbI3) represent a new class of light absorbers that have demonstrated tremendous progress in solar cell performance from 3.8% in 2009 to 20.1% in 2015. One attraction for perovskite halides is their bandgap tuning capability. For example, perovskite halide CH3NH3PbI2Br has a bandgap of about 1.8 eV, which makes it suitable for developing tandem or multijunction perovskite-based solar cells. However, perovskite halides have the capability of bandgap tuning by modifying their components building blocks. Moreover, high-efficiency perovskite solar cells can be made by low-cost processing methods. In addition, perovskite halides are not only direct-bandgap absorbers with strong absorption coefficients, but they also demonstrate long electron and hole diffusion lengths. For these and other reasons, perovskite halide solar cell technology is expected to attract strong interest from solar manufacturers and start-ups looking for their next-generation solar cell products.
However, current manufacturing methods typically produce unsatisfactory perovskite halide films. For example, many of the films produced are not full coverage, continuous films, free from pin-holes. In addition, it is very difficult to produce perovskite halide films that are highly crystalline and phase-pure; e.g. films that do not possess residual impurities such as lead iodide. Thus, there remains a need for both better performing perovskite halide films, and solar cells made therefrom, but also improved manufacturing methods for making high performance perovskite halide films.